Abstract
The automatic beats in crustacean heart, are maintained by impulses produced in the pace-maker which is consisted of ganglion cells. Such is called a neurogenic heart. Acetylcholine acts upon the neurogenic heart to accelerate the heart heart. The action potentials of both the ganglion cells in the pace-maker and of the cardiac muscle in Cambarus' heart were recorded simultaneously.
Acetylcholine increases strength of action potentials of cardiac muscle, without any effect on spike potentials of ganglion cells, both in frequency and amplitude. Eserine and DFP, which are inhibitor of cholinesterases, accelerates the action poentials of both ganglion cells and cardiac muscle. They are known to be able to penetrate into the neuron through the plasma membrane, but acetylcholine is nonpermeable.
Eserine and DFP, which inhibit cholinesterases in ganglion cells elevate the excitability of the pace-maker of neurogenic heart. Acetylcholine should play a role as a transmitter of impulses from nervous elements of the pace-maker to cardiac muscle. We think that the existence of the neuro-humoral mechanism is very probable in the neurogenic heart as in the myogenic heart.
